如何通过doInBackground方法android中的params在返回类型之间切换

Question

嗨，我正在开发一个http客户端，该客户端将处理我的android应用程序的所有url请求。我想要做的是能够调用我想要调用的特定方法。现在它所做的只是调用基本的httpUrlconnection。在这个类中，我有3个其他方法，我想根据调用它的内容来调用它们。这方面的任何帮助都将是伟大的：

以下是我如何调用方法：

 MyHttpClient task = new MyHttpClient(username, password);

如果我想用它登录网站的话。当我只想在没有密码的情况下使用它时，我会这样称呼它

MyHttpClient task = new MyHttpClient();

这些方法都有效，但我不知道如何调用其他三种方法。这是我做的课；

public class MyHttpClient extends AsyncTask<String, Void, String> {
private String username;
private String password;
//this is used if you need a password and username
//mainly for logins to a webserver
public MyHttpClient(String username, String password)
{
    this.username = username;
    this.password = password;
}
//used for image downloading
public MyHttpClient(){}

@Override
protected String doInBackground(String... params) {
    String url = params[0];
    return httpDownloadData(url);
}

//this is used for a simple http download of json files or xml file
//it must return a string fom the http request
private String httpDownloadData(String myUrl)
{
    String respone = null;
    HttpURLConnection urlConnection = null;
    try
    {
        URL url = new URL(myUrl);
        //put in the username and pssword for parmas to send to url
        //this is good for login
        if (username!=null)
        {
            Authenticator.setDefault(new Authenticator() {
                @Override
                protected PasswordAuthentication getPasswordAuthentication() {
                    return new PasswordAuthentication(username, password.toCharArray());
                }
            });
        }
        urlConnection = (HttpURLConnection)url.openConnection();
        InputStream inputStream = urlConnection.getInputStream();
        if(inputStream != null)
        {
            respone = streamToString(inputStream);
            inputStream.close();
        }
    }catch (IOException ie)
    {
        Log.d("IOExceptrion:", "In http downloader");
        ie.printStackTrace();
    }finally {
        if(urlConnection != null)
        {
            urlConnection.disconnect();
        }
    }
    return respone;
}
//this is to download images from HTTP connections
private Bitmap httpBitmapDownloader(String myUrl)
{
    HttpURLConnection urlConnection = null;
    try {
        URL url = new URL(myUrl);
        urlConnection = (HttpURLConnection)url.openConnection();
        urlConnection.setRequestMethod("GET");
        int statusCode = urlConnection.getResponseCode();
        if (statusCode != 200)
        {
            return null;
        }
        InputStream inputStream = urlConnection.getInputStream();
        if(inputStream != null)
        {
            Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
            return bitmap;
        }

    } catch (IOException e) {
        e.printStackTrace();
    }finally {
        if (urlConnection != null)
        {
            urlConnection.disconnect();
        }
    }
    return null;
}

//download strings via https
//Todo Add the certificate handler so turst server
// TODO: 4/4/16 BKS needed for this
private String httpsDownloadData(String myUrl)
{
    String respone = null;
    HttpsURLConnection urlConnection = null;
    //get the cert handler
    try
    {
        KeyStore keyStore = KeyStore.getInstance("");
        String algorithm = TrustManagerFactory.getDefaultAlgorithm();
        TrustManagerFactory tmf = TrustManagerFactory.getInstance(algorithm);
        tmf.init(keyStore);
        SSLContext context = SSLContext.getInstance("TLS");
        context.init(null, tmf.getTrustManagers(), null);
        URL url = new URL(myUrl);
        if (username!=null)
        {
            Authenticator.setDefault(new Authenticator() {
                @Override
                protected PasswordAuthentication getPasswordAuthentication() {
                    return new PasswordAuthentication(username, password.toCharArray());
                }
            });
        }
        urlConnection = (HttpsURLConnection) url.openConnection();
        urlConnection.setDefaultSSLSocketFactory(context.getSocketFactory());
       //urlConnection.setSSLSocketFactory(context.getSocketFactory());
        int statusCode = urlConnection.getResponseCode();
        Log.d("Status code: " , Integer.toString(statusCode));

        InputStream inputStream = urlConnection.getInputStream();
        if(inputStream != null)
        {
            respone = streamToString(inputStream);
            inputStream.close();
        }

    }catch (IOException e)
    {
        Log.d("downloading data: " , "in https webape");
        e.printStackTrace();
    } catch (NoSuchAlgorithmException e) {
        Log.d("Trustmanager issue:" , "Error");
        e.printStackTrace();
    } catch (KeyStoreException e) {
        Log.d("Keystore issues:", "Key needs att");
        e.printStackTrace();
    } catch (KeyManagementException e) {
        Log.d("Key management:" , "Key issue");
        e.printStackTrace();
    }
    return respone;
}
private Bitmap httpsBitmapDownloader(String myUrl)
{
    HttpsURLConnection urlConnection = null;
    try
    {
        KeyStore keyStore = KeyStore.getInstance("");
        String algorithm = TrustManagerFactory.getDefaultAlgorithm();
        TrustManagerFactory tmf = TrustManagerFactory.getInstance(algorithm);
        tmf.init(keyStore);
        SSLContext context = SSLContext.getInstance("TLS");
        context.init(null, tmf.getTrustManagers(), null);
        URL url = new URL(myUrl);
        urlConnection = (HttpsURLConnection)url.openConnection();
        urlConnection.setDefaultSSLSocketFactory(context.getSocketFactory());
        int statusCode = urlConnection.getResponseCode();
        if(statusCode != 200){return null;}
        InputStream inputStream = urlConnection.getInputStream();
        if(inputStream != null)
        {
            Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
            return bitmap;
        }
    } catch (MalformedURLException e) {
        e.printStackTrace();
    } catch (IOException e) {
        Log.d("bitmap download: " , "Https issues");
        e.printStackTrace();
    } catch (NoSuchAlgorithmException e) {
        e.printStackTrace();
    } catch (KeyStoreException e) {
        e.printStackTrace();
    } catch (KeyManagementException e) {
        e.printStackTrace();
    } finally {
        if (urlConnection != null)
        {
            urlConnection.disconnect();
        }
    }
    return null;
}
//this is used for downloading strings from an http or https connection
private String streamToString(InputStream is) throws IOException {
    StringBuilder sb = new StringBuilder();
    BufferedReader rd = new BufferedReader(new InputStreamReader(is));
    //add a fake parent to the line json data
    String line;
    while ((line = rd.readLine()) != null) {
        sb.append(line);
    }
    return sb.toString();
}

Answer 1

如果您想返回不同类型的结果，请从修改您的类定义

... extends AsyncTask<String, Void, String>

至

... extends AsyncTask<String, Void, Object>

由于String和Bitmap都是Object的子类，因此它将是有效的。当然，您仍然需要修改您的doInBackground(...)以返回Object。

Answer 2

调用

异步任务#执行（…）

有两个参数，其中第一个表示必要的方法，第二个表示其URL。或者将这两个param封装在一个类中。或者切换到android async http、Reform或Ion，因为现在没有人使用AsyncTask进行http。

Answer 3

您可以通过更优化的方式实现这一点。您应该为每个调用（不同的url）编写一个单独的异步任务。通过构造函数或asynctask的String参数管理参数。如有必要，将类设为抽象类，以便进行必要的更改。